For many years it has been the goal of microwave food designers to consistently control the heating of foods in a microwave oven so that the food absorbs the appropriate amount of energy in a given time period to reach a predetermined temperature. This has been done empirically requiring many hours of effort with often undesirable and unpredictable results. Design is even further complicated when multiple foods are to be heated together with each food attaining its own final temperature following its own time/temperature relationship. An example of a multi-component product is an ice cream, brownie and sauce product, wherein, the brownie and sauce would heat and the ice cream would remain relatively cold to provide a hot sundae.
Consistent, predicable disposition of energy or power (power is energy dissipation per unit time) within targeted areas of edible materials heated by microwave radiation has been an important and unattained goal for many years. It has been found that by partially surrounding the material to be heated with electrically conductive elements (in the art, usually called "shielding") one can under certain conditions as hereinafter described, obtain an unprecedented degree of control of the heating process. Specifically, a product comprised of one or more layers is placed in a structure or container which has at least one electrically conductive wall and whose cross-sectional shape might be circular, rectangular, ellipitcal, triangular, square, spaced apart or parallel plates, or any other convenient shape. This structure or container, which functions essentially as a waveguide, might be closed at one end with an electrically conducting closure element or it might be open. Its cross-sectional dimensions might be constant or variable. Surprisingly it has been found that by manipulation of product layer dimensions, position of a food product relative to the conductive manner, dielectric properties, and the dimensions and electrical conductivity of the waveguide structure one can consistently and predictably control the relative heating rates of the several components comprising the product to be heated.
U.S. Pat. Nos. 2,600,566 to Moffett and 2,714,070 to Welch both address controlled exposure by use of metal cups to control heating of the ice cream therein while the sauce heated. Further work in this art are exemplified by U.S. Pat. No. 4,233,325 to Slangan et al in which there is a completely metallic container with two compartments with the ice cream containing compartment being completely shielded by metal while the sauce containing compartment has a microwave transparent lid which allows the sauce to heat. Thus, it can be seen that the progress in this art has been to go back to completely metal-shielded portions and partially metallic-shielded portions to obtain appropriate heating results. Also, selective heating of products has been done by using metal shields with various size apertures over various portions of the food products contained therein to affect the heating thereof. However, the design of these shields and foods has been largely empirical and the lack of such products on the market probably indicates that such attempts have probably not been very successful.
Even though household microwave oven penetration has grown significantly in the last five years, very few food products have been successfully designed for use in the microwave oven, probably due to the lack of predictable behavior. Thus, even though microwave ovens are popular, the users of microwave ovens still find them objectionable because of the lack of reliably performing food products usable therein.
Therefore, it would be desirable to provide better control for the heating of food products in a microwave oven such that predicatable and consistent results can be obtained. Further, it has been desired for many years in the food industry to know how to design products without large amounts of R & D efforts both by people and in terms of cost to predict the behavior of foods while being heated in a microwave oven. Both of these have been long desired goals, but to date have apparently not been very successfully fulfilled and are objects of this invention. PG,5
The present invention overcomes the above difficulties by providing means and method for making food products for microwave ovens which provide predictable and understandable behavior.
An object of the present invention is to provide a method for manufacturing and designing food products with predictable performance for use in a microwave oven.
Another object of the present invention is to provide food products that consistently perform and are tolerant to heating in a microwave oven.
Another object of the present invention is to provide a method for making food products to be used in combination with conductive shielding in a microwave oven.